Prescription eyeglasses utilize a wide variety of lenses with several types of correction. Among the most common corrective lenses are bifocals, which have a full field lens with a zone in the bottom portion of each lens that corrects close range vision for reading. Depending on the needs of the wearer, the upper portion or zone of a bifocal lens may or may not correct for better long-range or distance vision. Unfortunately, for most bifocal wearers, neither the short-range correction nor the long-range correction of their glasses corrects sufficiently for the mid-range of vision. It is the mid-range of vision that is utilized when viewing a computer screen, piano music and many other tasks performed at about arm's length.
In trifocal lenses and in the more recently developed "progressive" lenses, there is a narrow zone that corrects mid-range vision. However, a computer user wearing such lenses must tilt his head up and down until the mid-range portions of his lenses are aligned with the computer screen. This corrects the user's vision, but often does so at the expense of the user's comfort and good body mechanics.
There is a need for auxiliary eyeglasses for temporary mid-range correction, which can be worn with the conventional lenses and only when needed, such as while using a computer or playing a piano. This eliminates the constant head tilting required when using the conventional lenses alone. There is a need for such auxiliary eyeglasses that provide a wide zone of correction, preferably across the full width of the lenses. There is also a need for such auxiliary eyeglasses that can be worn with the user's primary corrective eyeglasses. Further, there is a need for such auxiliary eyeglasses that are sturdy and inexpensive. Further still, there is a need for such auxiliary eyeglasses that are simple to attach to and remove from the primary eyeglasses in a manner that reduces the likelihood of damage to the primary lenses.